In a negligence action to recover damages for personal injuries, plaintiff appeals from a judgment of the Supreme Court, Nassau County (Young, J.), dated May 28, 1981, which dismissed his complaint following a jury verdict in favor of defendant on the issue of liability. Judgment reversed, on the law, and new trial granted on the combined issues of liability and damages, with costs to abide the event. On the facts in the record, it was not possible for plaintiff to sustain his burden of proof on the issue of liability without some showing of the severity of his injuries (see Naumann v. Richardson, 76 A.D.2d 917, app dsmd 54 N.Y.2d 680). At the trial, plaintiff testified that he was struck in the mouth by defendant's hand. Defendant admits striking plaintiff in the mouth but claims that he merely intended to push plaintiff away. The severity of plaintiff's injury is relevant to the issue of liability, in that such evidence would aid the jury in determining the force of the blow to plaintiff's mouth, and whether defendant's conduct was reasonable under the circumstances. Therefore, the trial court committed reversible error by excluding all evidence of plaintiff's injuries (see Bennetti v. New York City Tr. Auth., 22 N.Y.2d 742; Thorne v Burr, 41 A.D.2d 662; Naumann v. Richardson, supra). Gulotta, J.P., O'Connor, Thompson and Brown, JJ., concur.